AOAC 2018 Methods

B. Principle Products to be analyzed are suspended in water in tubes that are heated in a boiling water bath to dissolve the fructan. Sucrose in the sample is hydrolyzed at 30 o C by a specific sucrase enzyme (2), which has no action on lower degree of polymerization (DP) FOS, such as 1- kestose and 1,1-kestotetraose.

Starch and maltodextrins are concurrently hydrolyzed to maltose and maltotriose by pullulanase and α -amylase at 30 o C, and these oligosaccharides are then hydrolyzed to D- glucose by maltase (3).

D-Glucose and D-fructose are reduced at 40 o C by sodium borohydride to the corresponding sugar alcohols, D-sorbitol and D-mannitol (4). Native fructans and non-reducing FOS such as Neosugars ® are not affected by this reaction because they are non-reducing.

Fructans and FOS are specifically hydrolyzed by exo - and endo -inulinase and endo -levanase at 40 o C to D-glucose and D-fructose (5).

D-Fructose and D-glucose derived from fructan are measured using the PAHBAH reducing sugar method (6). This method is simple to use and the color response for D-fructose and D- glucose is the same (Figure 2018.07 ).

2